Method of securing grid wires



Feb. 10, 1931. GREBEL 1,792,219

METHOD OF SECURING GRID WIRES Filed Feb. 1), 1927 INVENTOR BRUNO GREBEL TORNEY Patented Feb. 10, 1931 UNITED STATES PATENT; OFFICE BRUNO GREBEL, OF BERLIN-SOHONEBEBG, GERMANY, ASSIGNOR 'IO SIEMENS & HALSKE,

AKTIENGESELLSCHAFT, 0F SIEMENSSTADT, NEAR BERLIN, GERMANY, A. CORPORA- TION' 0F GER-MANY METHOD or sncearive earn WIRES Application filed February 10, 1927, Serial No. 167,140, and in Germany February 27, 1926.

The present invention concerns discharge tubes comprising a control grid of the kind used in thermionic (hot-cathode) tubes. Tubes of the type now known to the art com-' prise a simple stretched-out filament which is disposed along the axis of the grid electrode and plate or anode surrounding it cylin drically. The grid consists of a wire of spiral shape. To insure greater mechanical strength, this spiral is mostly supported in such a manner that each turn is attached to one or more supporting wires.

This invention relates to an improved mode of securing the spiral to the supporting wires. In well-known control grids of the form hereinbefore described, the connection between the spirals and the supporting wires is established by welding. The welding method used involves the drawback that it is complicated from a technical viewpoint, and that it does not permit of the use of wires for the grid spiral of such thinness as would be desirable, on the ground that fine wires are liable to destruction in the welding process.

Now, according to the disclosure of the present invention, the grid spiral is united with the supporting wires by purely mechanical means, or to be more precise, by the application of a short pressure or sudden impact (blow). In the case of spiral-shaped grids, the method of manufacture consists in that the supporting wires, having any desired cross-section, preferably round or rectangular, are placed upon a cylindrical mandrel, the grid wire being spirally wound thereover. By the application of a short pressure or impacts along the supporting wires, the grid wires are driven into the supporting wires so that they come to be firmly united therewith. The same method may be applied similarly to grids of other shapes and nature, for instance, plate-shaped corners.

This method of attachment, preferably, is predicated upon the fact that the grid wire and the supporting wire are of different hard-- ness for instance, the best plan is to make the supporting wire of a soft material, such as nickel, whereas the spiral wire consists of hard tungsten. Under these conditions it will be an easy thing to drive the grid wire so This newmethod of grid anchoring offers the advantage that it turns out to be very cheap and convenient in large-scale manufacture. The chief advantageous feature'of the grids is that the spirals can be made of very fine wires. This, in turn, has the further merit in the case of high-vacuum tubes that the degasification ofothe tube is promoted, and that the controlling action of the grid upon the electron paths is diminished,,whereby the use of lower plate potentials is possible as comparedwith tubes in which grid wires of the thickness as'heretofore usual are mounted. For example the method here disclosed makes it possible to employ tungsten wires of 0.05 mm. for the grids in amplifier tubes, and these may be attached to an anchor wire made of nickel of 0.5 mm. thickness. The present method further offers the advantage that for the building of the grid, materials may be used which are not uniteable by welding.

The invention will be more clearly understood with the aid of the accompanying drawings.

a In the drawings, Figure 1 represents the electrode assembly of a three electrode tube, with the anode broken away to show the filament and grid more clearly.

Figure 2 shows a plan view of the grid and filament electrodes of Figure l.

Figure 3 shows a longitudinal cross section through the grid supporting means of F igures l and 2. a

Figure 4 shows a modification of the grid electrode. 7

Asshown in the drawings, the grid electrode 3 of Figures 1, 2, and 3 is in the form of a helix. The grid 3 may be made of very fine wire and may comprise materials which are not suitable for welding. Each of the turns of the grid electrode 3 is embedded in a supporting rod 4 which consists of a material such as nickel, which is softer than the material of the grid electrode. The turns of the grid are embedded in the supporting rod 4 by the application of a. sudden impact or blow. This blow causes the softer material of the supporting rod 4 to flow about the harder material of the grid and to firmly unite therewith. It is obvious that the turns of the grid may have a cross section other than round, although a round cross section is economical. It is also apparent that the supporting rod 4 may have other forms than that shown. A filament 2 is positioned within the grid 3, and this filament may comprise the straight cathode, as shown, the hairpin yp types known in the art. Additional electrodes such as grids may also be employed.

As shown in Figure 4, the grid comprises a spiral, and each ofithese turns is embedded in the supporting rod as in the caseo-f the helix. In the case of both the helix and the spiral, each turn is embedded in the softer supporting rod at a definite space relation with the other turns.

Having thus described my invention, I claim: 7

1. A grid electrode comprising a wire heliX secured to a support member by having portions of the turns of the helix compressed so as to displace sufiicient material of the support member to embed the said portions in the support member and hold the turns of the helix in fixed spaced relation.

2. The method of producing a gridstructure which comprises winding a fine wire of relatively hard metal into helical form, disposing a rod of relatively soft metal contiguous to the turns of the helix, and applying pressure to cause a portion of each of the said turns to displace the metal of said rod to embed the turns therein for retention definite space relation.

In testimony whereof I aflix my signature.

BRUNO GREBEL.

the indirectly heated type, or other 

